In this proposal I plan to investigate the formation and function of the synaptic bouton at the Drosophila NMJ. The control of the differentiation of the synapse presynaptically is poorly understood. One manifestation of this differentiation is the formation of the synaptic bouton. Synaptic boutons are found at nearly all synapses but the formation of these varicosities as well as their function has not been addressed experimentally. Preliminary data from the novel Drosophila gene nerve-wracked suggests that this gene specifically controls the formation of boutons at the NMJ. I plan to further characterize this gene and use this reagent to investigate the formation and function of synaptic boutons.